Understanding Lebesgue Measure: Example of Open Intervals on [0,1]

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SUMMARY

The discussion centers on the Lebesgue measure, specifically addressing the Lebesgue outer measure of rational numbers within the interval [0, 1]. It is established that the Lebesgue outer measure of the rational numbers is indeed 0, leading to the conclusion that there exists a set of open intervals whose union contains all rational numbers in [0, 1] while maintaining a total length of less than 1. The user initially expressed confusion but later resolved their query independently.

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  • Understanding of Lebesgue measure and its properties
  • Familiarity with open intervals in real analysis
  • Knowledge of set theory and unions of sets
  • Basic concepts of measure theory
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tomprice
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I am confused about lebesgue measure.

I have heard that the lebesgue outer measure of the rational numbers is 0.

So could someone please give an example of a set of open intervals such that:

a. The union of these intervals contains the rational numbers on [0, 1]

b. The sum of lengths of these intervals is less than 1.

The definition of lebesgue outer measure implies that, if the lebesgue outer measure of the rationals is 0, then such a set of open intervals must exist. But I am flabberghasted as to how this could be so.

Thanks very much in advance.
 
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